Method of and apparatus for reconditioning grinding disks



Nov. 11, 1941. R. c. HANSEN 2,262,583

METHOD OF AND APPARATUS FOR RECONDITIONING GRINDING DISKS Filed May 31, 1941 2 Sheets-Sheet l 0G0 OCL OO Y w th, I 3} "I Poet/Q7 (HA/5 HA/VJf/V Nov. 11, 1941. R. c. HA NSEN 2,262,583

METHOD OF AND APPARATUS FOR RECONDITIONING GRINDING DISKS Filed May 31, 1941 2 Sheets-Sheet 2 Patented Nov. 11, 1941 UNITED STAT-ES PATENT OFFICE rinrnon g r am) srrsnsros roe. RECON- ONING' GRINQING DISKS f Robert Chris mm, Chicago, n1. 7 Application May 31, 1941, Serial No. 395,960

8 Claims. 101. 51-293) In the past it has been the practice to use a flat grinding disk on a grinding head in connection -with the refinishing and repainting of automo-' bile bodies and fenders. Such a grinding disk or plate has had a very limited life due to the grinding points thereof becoming account of the abrading surfac becoming clogged with foreign material such as aint, enamel, and the like.

An object of the present inve tion is to provide a method of and apparatus for processing flexible grinding disks whereby the cutti g and grinding quality of the abrasive surface t ereon is greatly improved.

Another object of the presentiinvention is to provide a method of and an ap aratus for reconditioning grinding disks so that they could be at, as well as on re-used and thus materially cut down the cost of the refinishing work.

By the use of the present invention I have found that I have been able to cut down the grinding cost as much as fifty per cent, since grinding disks reconditioned in accordance with this invention have had their usefulness increased at least fifty per cent,

In accordance with the general feature of this invention, there is provided in a method of reconditioning a fiat grinding plate or disk, comprising a fibrous sheet having a coating of abrasive material on an outer side thereof, thestep of indenting the rear and uncoated side of the sheet at a, plurality of points to bulge outwardly on the coated side worn and flattened abrasive points whereby these bulged portions will become effective as abrading areas in the re-use of the grinding plate, as well as to loosen foreign material embedded in the abrasive coating.

In accordance with other features of my invention, I provide an apparatus for reconditioning a fiat grinding disk or plate which includes a holder for the grinding plate having a relatively soft surface on which the coated side of the plate is adapted to rest, and having a member above the other and uncoated side of the plate for indenting the. same-at a plurality of points to bulge portions of the coated side downwardly against the surface. I a i e Other objects and featuresof this invention will more fully appear from the following deaccompanying drawings of an embodiment of the invention, and in which:

Figure 1 is a plan view of an apparatus for practicing the invention showing a grinding disk in position in the apparatus Figure 2 is a side view of the apparatus shown in Figure 1 showing how a striking pin is insertable in the top member, as well as showing a portion of the hammer for striking the pin;

Figure 3 is an edgewise view of a fiat grinding ing diagrammatically an arrangement of the grinding points;

Figure 6 is a diagr mmatic fragmentary sectionalview similar Figure 5 showing how the grinding points ome .nat and how the coating becomes clogged after the disk has been used:

Figure 7 isa"fragmentary/diagrammatic cross sectional view through a portion of a disk shown Figure 10 is a cross sectional view takenalong the lines X-X of Figure 8;

Figure 11 is a top plan view of a modified form of an apparatus for practicing the invention; and

* Figure 12 is a side elevational view of the ap-- paratu shown in Figure 11.

As shown on the drawings:

I have in the accompanying drawings designated'the grinding disk or plate generally by the reference character ll. This disk is of wellknown construction in the art and includes a backing of sheet material which may be flexible and which usually comprises a disk of fibrous materiaL- I have designated the fibrous or fiextailed description taken in connection with the ible, backing by the reference character H, and I have designated the abrasive coating by the reference character it.

of any usual or conventional material, such, for example, as emery or the like. Also, the disk is usually provided with a central aperture I8 by This coating is on the 1 outer exposed side of the disk in use and may bev means of which the disk is fastened to a grinding head for rotating the disk against the work to be finished or treated.

In Figure 5, I have more or less shown schematically in section the condition of the abrading points of the abrasive coating of the disk prior to the use of thedisk.- In Figure 6, I have illus.- trated the condition ofthe abrading points'or areas of the abrasive coating after the disk has.

been used.

Initially the grinding points or areas, as shown schematically in Figure'5, are relatively sharp and are effective for an abrading operation.

After the disk has been'used for a given length of time, these points I5, as shown in Figure 6, become flattened, and the spaces between the abradingpoints become clogged with foreign material, such as paint, metal, or the like, as designatedby-thereference character [6.

When the grinding disk assumes the condition shown ,diagrammaticallyin Figure 6, it hasv been Ithe ..'pract iceheretofore to throw thedisk away. Since these disks are quite expensive, it will, of

course, be appreciated that a great saving-will beeffected if these disks can bereconditionedand used-over againfor any length oftime. v Asnoted beforeI have found that by the use of my inyentio'n ms feasible to cut down the costof the grinding disks at least fifty, percent or, in other words, to increase their life by at least fifty percent. j.

Injaccordanc'e with the features of this invention, afterthe grinding disk'has reached the stage shown diagrammatically in Figure 6, it is placed in an apparatus of my invention shown in Figures 1 and 2. This apparatus includes a base I8 .havinga relatively soft top surface H which may comprise a layer of wood as shown or may be of any other relatively soft material. grinding disk It to be reconditioned is placed with-..its coated area downwareLor, in other words, against the wood block ll.

' Thereafter a cross-shaped member, I8 is placed gongtop :ofthe wooden member II. "This crosslike'member I 8 includes four ofiset legs I;9 for restinggagainst the wooden member I1 and to support the radial arms of the cross-shaped The"v member in spaced relation to the uncoated or rear sidell of the grinding disk Ill disposed thereunder V Each of the radial arms of member l8, as

shown in Figure 1, is perforated or provided with pin holes 20, each of which is adapted to have inserted therein a striking pin 2| (Figure 2).

It will, of course, be appreciated that I-have illustrated my invention in its simplest form,

,particularly with reference to the apparatus. In

Figure 2, I have shown thatthe striking or bluntv pin 2| is adapted to be hit'by a hammer desig-j nated generally by th'e reference character 22.

It is, of course, clear that a plurality of the pins,

21 may be inserted in all of the apertures 20 at the same time and all of the pins may be struck bya suitable striking member such for example,

' and in this manner the plate 32 is prevented from I leasable, rotatable engagement.

as the head ofa drill press or the like. In other;

words, any suitable means may be employed for tapping the pins in'o'rder to indent Va flexible layer H of the grinding disk, as shown in Fig.-

ures 4 and 7-, The indentations are designated.

generally byjthe reference character 25. Any number of these indentations 25 may be made i in theuncoateci side of the grinding disk in ac-* cordance with the particular desires of the'person reconditioning the disk.

The indentations 25 result in bulging outwardly, as designated at 26 in Figure 7, of spaced areas of the grinding points of theabrasive coating l2. These bulged points 26 become high points in the abrasive coating and, of course, thus become'efiective for use ingrinding operations. I also find that by reason-of the indenting of the disk'foreign material l6, such as paint a or the like embedded between the'points of the abrasive coating, becomes loosened, so that when the disk is reused such material tends to become dislodged from the abrasive coating.

Now if, for example, four lines of indentations 25 as shown in Figure 4 are made in the grinding disk, the disk maybe used until the bulged points provided therefcr become worn ofi or fiat. Then the disk can again be subjected to my reconditioning., oper ation. This operation can be repeated 'at'interjvals. or until such time as the abradin'g points have become worn to such an extent that the abrasive coating is no longer *effectiye for grinding purposes.

It will bereadily understood that, in the us of the apparatus -shown in Figures 1 and 2, the step of forming bulges in the abrasive surface 01" the disk I0 may be performed merely once to attain the result shown in Figure 4, that is, a. plurality of bulges 25 extending along two diameters of the disk. If desired, however, the formation of the bulges by impressing the pins 2| against ,the back of the disk may be repeated several times, the disk I0 being rotated in the apparatus shown in Figure between each of the operations with the result that the disk may be covered with impressions 25 to the degree desired.

f. In the form of apparatus shown in Figures 8 and 9, ther'eis provided a suitable base member 21 upon which is mounted a resilient block 28 which isv adapted to receive the disk to be processed with the abrading surface down as hereinbefore'described. ,A suitable upstanding supporting frame 29 extends upwardly and bridges the base 21 and is suitably secured thereto as by feet 30 which receive bolts 3| which are secured to the base member. The member 29 is provided with substantially vertical side portionswhich serve as guide or alignment members for a plate 32 into which depending studs 33 are secured. The

plate 32 is provided with substantially diametrically opposed lugs 32a,which are slotted to receive the vertical portions of the member 29,

be seen that rotation of the handle 31, will rotate the spindle 35, and due to the threaded engagement with the enlarged portion 36 of the frame 29 the plate 32 will be raised or lowered. and.

when adisk to be processed is placed upon the block 28 with the abrasive surface down. the members 33 may be embedded in the disk to create the bulges heretofore discussed.

The-modified apparatus disclosed in Figures 11 and I2 constitutes a suitable base .38 having a standard 39 formed on one side thereof and a bracket 40 formed on the other side thereof. The standard 39 is' provided with a central vpin 4| which is adapted to receive the central aperture of a disk to be treated.

The bracket 40 is provided with an angular extension 41 which'extends in the direction of the standard 39 and upon which is rotatably mounted a cone 42 formed from any suitable resilient material, such as, for instance, rubber. The upper end of the bracket 40 is provided with a bifurcation which affords apertured lugs 43 between which an arm 44 similarly apertured at its lower end may be secured as by a pivot pin 45. The arm 44 terminates at its upper end in a sleeve 46 through which extends a Journal having a crank arm 41 secured at its upper end and a conical member 48 secured at the lower end thereof in substantial alignment with the resilient cone 42. The cone 48 is, like the plate 32 in Figures 8 and 9, provided with suitable studs or pins 33 which are adapted to be pressed against the rear face of a disk to be processed, thereby creating bulges in the emery face thereof.

As will be seen from Figure 12, when a disk It) is mounted on the pin M, the arm 44 and sleeve 46, with their appurtenances, may be raised about the pivot pin 45, whereby the disk In may be positioned to overlie the cone 42.

Thereafter the arm 44 may be lowered to bring the cone 48 into alignment with the cone 42, and preferably a suitable locking element 49 is provided whereby the arm 44 is maintained in its lowermost position. Thereafter the crank 41 may be rotated to impart rotation to the cone 48, the disk Ill, and the cone '42. It will be understood that by operation of the crank 41 as above described the desired bulges will be imparted to the disk very quickly and easily, whereupon the lock 49 may be released, the arm 44 raised, and the processed disk I removed from the pin 4|.

I claim as my invention:

1. In a method of reconditioning a flat grinding plate made of flexible sheet material with a coating of abrasive on an outer side thereof, the step of bluntly striking the plate at a plurality of points on its non-abrasive side to bulge portions of the abrasive side outwardly and thus to loosen foreign material embedded in the abrasive coating.

2 In a method of reconditioning a fiat grinding plate comprising a fibrous sheet having a coating of abrasive material on an outer side thereof, the step of indenting the rear and other side of the sheet at a plurality of points to bulge outwardly on the coated side worn and flattened abrasive points whereby said bulged portions will become effective as abrading areas in the re-use of the grinding plate.

3. In an apparatus for reconditioning a flat grinding plate of the type comprising a fibrous sheet having a coating of abrasive material on one side thereof, a holder for the grinding plate having a relatively soft surface on which the coated side of the plate is adapted to rest and means above the rear and uncoated side of the plate for indenting the same at a plurality of points to bulge portions of the coated side downwardly against saidsoft surface.

4. In an apparatus for reconditioning a flat grinding plate of the type comprising a fibrous sheet. having a coating of abrasive material on one side thereof, a holder for the grinding plate having a relatively soft surface on which the coated side of the plate is adapted to rest and means above the rear and uncoated side of the plate for indenting the same at a plurality of points to bulge portions of the coated side downwardly against said soft surface, said means including a member having a plurality of pin holes in each of which a striking pin is insertable for indenting the uncoated side of the plate.

5. The method of processing a flat grinding plate made of flexible material with a coating of abrasive on one surface thereof which includes indenting the. surface of said plate rei mote from that having the coating of abrasive at localized areas to provide impressions thereon and bulges in the'surface covered by the abrasive, and impressing said indentations sufficiently deep so' that the bulges are retained in the flexible sheet material.

6. man apparatus for reconditioning a flat grinding plate of the type comprising a flexible sheet having an abrasive coating on one surface thereof, means for mounting said plate for processing, said means including a relatively soft surface against which said abrasive surface is adapted to rest, a supporting assembly, said assembly including a supporting element arranged to bridge said mounting means, a studded plate adapted for movement toward and away from said mounting means to bring the studded surface thereof into engagement with the back of the disk, a threaded spindle element secured to means and being adapted for rotation over the.

other surface of said grinding element in opposition thereto, and means for rotating said disk between said backing means and said indenting means.

8. In an apparatus for processing a grinding element having an abrasive surface, a support, a standard mounted on said support, said standard being adapted to rotatably receive said grinding element, a bracket on said support, a backing member rotatably mounted on said bracket and being arranged to engage the abrasive sur-* face of said grinding element when. the latter is mounted on said standard, an indenting member rotatably mounted on said bracket and being arranged to engage the opposite surface of said grinding element in opposition to said backing member, means for urging said backing member and said indenting member together with said grinding element therebetween, and means for imparting rotation to said backing member and said indenting member:

' ROBERT CHRIS HANSEN. 

